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On strontium and barium anomalies in the sediments of Charkadio Cave (Tilos Island, Dodekanese, Greece)

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The sediments of Charkadio Cave (Island of Tilos) have been object of chemical and mineralogical investigation. Sampling the speleothems of Charkadio Cave, it is possible to look back into the island’s younger geological history. Tilos is of non-volcanic origin but neighbored to several volcanoes of the Aegean (Kos, Nisyros, and Giali). We observed a certain coincidence of increased Ba and Sr values in such samples and volcanic activity. Some of the layers of these fine-grained sediments contain volcanic particles (ash grains and lapilli). Interestingly, these strata have the highest content of Ba and Sr, as determined by neutron activation analysis. Additionally to this discovery, Sr-rich barite crystals were found in some of these layers. Thus, Ba and Sr must either exist on the surface of tephra particles in volatile and water-soluble compounds and/or were released by weathering from Ba and Sr containing feldspars (originating from pumice) in the cave sediment environment. Since other cave sediments from Tilos, which were not exposed to volcanic products, contain very much lesser quantities of Ba and Sr, we conclude that mobile Ba and Sr compounds are contributed to the sediment by volcanic fallout.
... The high concentration of ferromagnesian like trace elements (V and Ni) in the sediments could be due to the weathering of amphibolites, or to its preferential incorporation into clay fractions (Das et al. 2006) or to heavy mineral accumulation into coarse-grained fraction (Wu et al. 2013). The weathering of feldspars induces the depletion of alkali trace elements such as Ba and Sr (Steinhauser et al. 2008) but both elements were accumulated along the profiles. The high Ba contents in the sediments might be a result of the source rock nature and the regime of surface processes while the high Zr content is related to the high proportion of zircon derived from felsic protolith as is the case reported by Ndjigui et al. (2019). ...
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... These sediments have mostly been classified as shales and accessory as wakes and litharenites in the discrimination diagram (Fig. 17). Generally, the weathering of feldspars induces the depletion of alkali trace elements such as Ba and Sr (Steinhauser et al., 2008) but both trace elements were accumulated along the terraces. The high Ba contents might be a result of the source rock nature and the regime of the surface processes. ...
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Reviewing the current status of real-time correction of counting losses in nuclear pulse spectroscopy, the pileup problem is identified as the last question not resolved satisfactorily up to now. Correction of pileup losses in provided, at least in principle, by the classical pulse generator method, however, severe limitations in test frequency prohibit its application to real-time correction of counting losses. A solution is offered by the novel principle of the virtual pulse generator which obviates the shortcomings of the classical method simply by not introducing pulses into the spectroscopy system. Instead, the probability for pileup-free pulse processing is determined by suitable tests of the system status at arbitrarily high test frequencies. After a discussion of the principles of the new method and its application to a real-time correction system experimental evidence is provided for the complete correction of counting losses of more than 98% under conditions of stationary as well as variable counting rates up to the limit of stable operation of the underlying spectroscopy system which is 800 000 c/s for an experimental high-rate gamma spectrometer.